The subject of the present invention is a novel cathode which can be used in electrolysis. It also relates to a process for the manufacture of this cathode. It relates especially to a cathode which can be used in the electrolysis of an aqueous solution of an alkali metal halide, especially remarkable for the low value of its operating potential and for the stability in time of its electrochemical performances.
This cathode belongs to the group of activated, metallic cathodes which are obtained by coating a cathodic substrate by means of various activating materials, essentially aimed at reducing the hydrogen overvoltage in an alkaline medium.
European Patent Application No. 0,129,374 describes cathodes carrying a coating consisting of a mixture of at least one metal of the platinum group and at least one oxide of a metal of the platinum group; the metal of the platinum group representing 2 to 30% of the weight of the said mixture.
Japanese patent application published under No. 57-13,189 describes a nickel or nickel alloy cathode carrying a coating which consists of a metal of the platinum group or an oxide of the said metal.
British Patent No. 1,511,719 describes a cathode consisting of a metallic substrate, a coating of cobalt and a second coating of ruthenium.
U.S. Pat. No. 4,100,049 describes a cathode which consists of a substrate and a coating consisting of a mixture of a precious metal oxide and a semiconductor metal oxide, especially zirconium oxide.
The Japanese patent application published under the number 54-090,080 describes a technique for the manufacture of a cathode which consists in treating a ferrous substrate with perchloric acid and then coating this cathode by fritting with active substances containing ruthenium, iridium, iron and nickel in the metallic form or in the form of a compound of the metal.
A technique for depositing a coating consisting of a nickel-palladium alloy on a substrate, for example, consisting of nickel, is also described in the U.S. Pat. No. 3,216,919. According to this patent, a coat of the alloy in the form of a powder is applied on the substrate and fritting of the said alloy powder is then carried out.
The coating of an electrode by electroplating with a ruthenium-nickel alloy has also been proposed (Russian Patent No. 264,096).
Japanese patent application published under the number 54-110,983 (U.S. Pat. No. 4,465,580) describes a cathode which carries a coating consisting of a dispersion of particles of nickel or a nickel alloy and an activator consisting of platinum, ruthenium, iridium, rhodium, palladium, or osmium or an oxide of these metals.
Japanese patent application published under the number 53-010,036 describes a cathode which has a semiconductor metal substrate and a coating of an alloy of at least one metal of the platinum group and a semiconductor metal and, if appropriate, a surface coating of at least one metal of the platinum group.
European Patent Application No. 0,129,734 describes a technique for cathode manufacture, by depositing on an electroconducting substrate, a coating solution containing a metallic oxide precursor and necessarily, a cleaning agent with a view to dissolving the most soluble parts of the substrate and/or a coat of the coating with is already deposited. This technique additionally consisting in an operation for the removal of the most volatile part of the coating solution, the said part containing the solubilized fractions of the substrate (op. cit. p. 14).